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PubMed1990

Computerized estimation of size of nucleic acid fragments using the four-parameter logistic model.

We have developed improved methods for statistical estimation of the size of linear duplex DNA after continuous- or pulsed-field electrophoresis in agarose and polyacrylamide gels. We employ the four-parameter logistic model to describe the smooth, symmetrical, sigmoidal relationship between electrophoretic mobility (distance migrated) and log of molecular size (kb): distance = a - d/1 + (size/c)b + d. The four parameters (a,b,c,d) are estimated by nonlinear least-squares curve fitting using the Marquardt-Levenberg algorithm, where a represents an upper plateau, b a slope factor, c the midpoint, and d the lower plateau. Estimates of size for unknown species are accompanied by estimates of the standard error (SE) or coefficient of variation (%CV). A plot of SE and %CV versus size results in a "precision profile" which objectively defines the useful range of the calibration curve. This logistic relationship is more general than the rectangular hyperbola or linear methods, provides excellent goodness of fit, and can be used as a "global" method for the entire calibration curve, rather than as a "local" method for small segments of the curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Calibration↗

PubMed1990

Identification of high risk groups for breast cancer by means of logistic models.

In order to identify high risk groups for breast cancer, unconditional multiple logistic regression models based on 5 widely recognized and easily identifiable risk factors (age at menarche, at menopause and at first birth, family history of breast cancer and body mass index) were applied to a large dataset including 2085 cases and 1936 controls aged 50 or over derived from two unmatched hospital-based case-control studies conducted in Italy. Although various models provided an excellent fitting, both on the whole dataset and using a training-testing approach to a priori identified separate subset, the observed extent of variation in breast cancer risk between highest and lowest decile of the distribution was limited to a factor 2. This indicates that the 5 variables considered did not allow identification of subgroups with substantially elevated risk of breast cancer to have practical implications for screening/prophylactic treatment purposes.

Adolescent↗

PubMed1981

The Hamilton depression scale. Evaluation of objectivity using logistic models.

The consistency of the Hamilton Depression Scale (HDS) as a measure of the severity of depressive states has been examined when the scale was used weekly during a trial when imipramine. By use of logistic models (Rasch) the consistency of the HDS has been considered across patient-variables as age, sex, plasma levels of imipramine, and diagnosis. The results showed that the original 17-item HDS was without adequate consistency, i.e. the total score of the sample of items was no one-dimensional measure of depressive states. However, a melancholia subscale of the HDS contained items the total of which can be used to compare patients quantitatively, although in some part of the analysis one of these items showed ceiling effect. It was concluded that the melancholia subscale (containing the items depressed mood, guilt, work and interests, retardation, psychic anxiety, and general somatic symptoms) can form the basis for further improvements in the field of quantitative rating scales for depressive states.

Adult↗

PubMed1992

A multiple logistic model for predicting the occurrence of Campylobacter jejuni and Campylobacter coli in water.

A multiple logistic regression model was established to predict the occurrence of Campylobacter jejuni/coli, related to index bacteria such as faecal coliforms, faecal streptococci, and sulphite-reducing clostridia, in a water source in southern Norway. The fitted model indicated that faecal coliforms were strong predictors for C. jejuni/coli, although the water temperature also had a strong influence on results. Sulphite-reducing clostridia, faecal streptococci, and season of the year had no significant influence on the results, in spite of their apparent predictor value as separate variables. The model employed offers a new approach to the relationship between index bacteria and the occurrence of pathogenic bacteria in water. Similar models can also be established in general food microbiology.

Campylobacter↗

PubMed2000

Calibration and LOD/LOQ estimation of a chemiluminescent hybridization assay for residual DNA in recombinant protein drugs expressed in E. coli using a four-parameter logistic model.

Calibration is the process of fitting a model based on reference data points (x, y), then using the model to estimate an unknown x based on a new measured response, y. In DNA assay, x is the concentration, and y is the measured signal volume. A four-parameter logistic model was used frequently for calibration of immunoassay when the response is optical density for enzyme-linked immunosorbent assay (ELISA) or adjusted radioactivity count for radioimmunoassay (RIA). Here, it is shown that the same model or a linearized version of the curve are equally useful for the calibration of a chemiluminescent hybridization assay for residual DNA in recombinant protein drugs and calculation of performance measures of the assay.

Calibration↗

PubMed1993

Influences upon attendance at out-patient facilities--the contribution of linear-logistic modelling.

The research on attendance at out-patient psychiatric facilities has produced conflicting evidence that provides little guidance for the practitioner. It is suggested that inadequate data exploration could explain some of the discrepant findings. Analyses of multi-way tables using linear-logistic models were undertaken to demonstrate patterns of association that cannot be revealed through the use of simple chi-square tests on two-way contingency tables. The variables chosen for these analyses were those that have produced conflicting findings in the literature on children's attendance at child guidance facilities.

Adolescent↗

PubMed2006

Relationships between independence level of single motor-FIM items and FIM-motor scores in patients with hemiplegia after stroke: an ordinal logistic modelling study.

OBJECTIVE: To assess the relationships between independence levels of single motor-related Functional Independence Measure (FIM) items and summed FIM-motor scores of patients with hemiplegia after stroke. DESIGN: For each patient FIM scores were assessed 4 times during hospitalization. Ordinal logistic analyses were performed on group data. SUBJECTS: Fifty patients with hemiplegia after stroke staying in a long-term rehabilitation facility. RESULTS: Analyses revealed that FIM-motor scores accounted for much of the variability of independence levels for most of the single FIM items, including dressing upper body, and transfers to bed/chair/wheelchair and to toilet. For these items, the independence levels were proportionally associated with FIM-motor scores. For eating, higher FIM-motor scores (>60) were associated with modified independence and lower FIM-motor scores (<40) correlated with attainment of supervision/set-up levels. For dressing lower body, greater independence was apparent when FIM-motor scores were higher (>60). CONCLUSION: For single FIM items, relative difficulty was comparable with results from previous literatures using Rasch analyses. Moreover, our results revealed that relative difficulty for single items varied greatly between independence levels. With regard to disability task targets, probability of independence evaluated from logistic modelling is an aid to efficient rehabilitation scheduling.

Activities of Daily Living↗

PubMed1989

Prognostic factors influencing cisplatin-induced emesis. Definition and validation of a predictive logistic model.

Data obtained from 209 patients who entered different prospective randomized antiemetic trials were analyzed to establish the prognostic value of some variables on the control of cisplatin-induced emesis. The antiemetic regimens evaluated included the following: metoclopramide (M) at 1, 2, and 4 mg/kg total dose and a combination of M (4 mg/kg) with dexamethasone (D) (40 mg). Vomiting lasting more than 1 hour (no protection [NP]) was the endpoint selected for the analysis. A logistic model carried out, first on the 110 subjects receiving the M + D regimen and then on the whole sample, selected sex (P = 0.0001), Eastern Cooperative Oncology Group performance status (PS) (P = 0.006), and age (P = 0.01) among the six factors considered. Since the prognostic value of these variables is mostly related to their interaction, three major risk classes were identified. The corresponding NP rates were 26.3%, 42.4%, and 70.8% for the low-risk, intermediate-risk, and high-risk groups, respectively (P = 0.000002). Except for the lowest M level, the observed NP rates were significantly associated to the risk classes, whereas the antiemetic regimen influenced the antiemetic outcome only in the low-risk class. Regardless of the regimen employed, certain patient characteristics, such as sex, PS, and age, significantly affect cisplatin-related emesis and should be carefully considered in planning further studies.

Adult↗

PubMed1987

Use of a four-parameter logistic model to evaluate the protein quality of mixtures of Mormon cricket meal and corn gluten meal in rats.

Weanling Sprague-Dawley rats were fed diets containing corn gluten meal (CGM), Mormon cricket meal (MCM), MCM supplemented with methionine (MCM + Met) or CGM-MCM mixtures as the sole source of dietary protein in purified diets. Animal response (weight or nitrogen gain) was analyzed as a function of nitrogen intake and described by a series of curves using a four-parameter logistic model. Parameter sharing was used to differentiate statistically between the response curves. When used for maximum nitrogen retention the quality of the protein sources could be ranked as follows: MCM + Met greater than 40 CGM-60 MCM greater than 50 CGM-50 MCM greater than 60 CGM-40 MCM greater than MCM greater than CGM. When used for maximum weight gain the ranking was as follows: MCM + Met greater than 40 CGM-60 MCM greater than 50 CGM-50 MCM greater than 60 CGM-40 MCM greater than MCM greater than CGM. The rankings of the protein sources when used for weight maintenance or nitrogen equilibrium were similar to those seen for maximum weight or nitrogen gain except for the ranking of MCM, which changed from fifth to first. These results show MCM to be a good quality protein source and that methionine is the first limiting amino acid when used for growth but not for maintenance. The shape of the response curves was dependent upon the response criteria as well as the source of dietary protein. The factors that may affect the shape of the dose-response curves and the application of nonlinear models toward animal feeding programs are discussed.

Animal Nutritional Physiological Phenomena↗

PubMed2003

An appraisal of multivariable logistic models in the pulmonary and critical care literature.

OBJECTIVE: Multivariable modeling techniques are appearing in today's medical literature with increasing frequency. Improper reporting of these statistical models can potentially make the results of a study inaccurate, misleading, or difficult to interpret. We performed a manual literature search of five international pulmonary and critical care journals to determine the accuracy in the reporting of logistic regression modeling strategies. DESIGN: We examined all of the published manuscripts for 12 potential limitations in the reporting of important statistical methodologies over a 6-month period from July 1, 2000, until December 31, 2000. RESULTS: Of the 81 articles that included multivariable logistic regression analyses, only 65% (53 analyses) properly reported the coding classification of pertinent independent variables that were included in the final model. An odds ratio and confidence interval were reported for the independent variables included in the final model for 79% (64 analyses) and 74% (60 analyses), respectively. Only 12% (10 articles) referenced whether interaction terms or effect modifications were examined, 1% (1 article) reported testing for collinearity, and only 16% (13 articles) included a goodness-of-fit analysis of the logistic model. The type of statistical package was reported in 69% (56 articles). Finally, approximately 39% of the articles (22 of 57) may have overfit the logistic regression model, leading to potentially unreliable regression coefficients and odds ratios. CONCLUSIONS: Our results indicate that the reporting of multivariable logistic regression analyses in the pulmonary and critical care literature is often incomplete, therefore making it difficult for the reader to accurately interpret the manuscript. We recommend the implementation of adequate guidelines that will lead to overall improvements in the reporting and possibly to the conducting of multivariable analyses in the pulmonary medicine and critical care medicine literature.

Critical Care↗

PubMed1983

Logistic models for prediction of enteric morbidity in the treatment of ovarian and cervical cancers.

To identify patients at high risk for the development of enteric injury, an analysis was made of 212 women who received extensive pelvic and abdominal radiotherapy at the University of Minnesota from 1970 through 1981. One hundred one patients with cervical carcinomas received 8,000 to 8,500 rads to point A, 6,000 rads to point B, and 4,500 to 5,075 rads to the periaortic lymph nodes. One hundred eleven women with ovarian cancers received 2,000 rads to the entire abdomen, followed by an additional 2,975 to 3,000 rads to the pelvis. The overall complication rate was 6.6% (14/212). The only patients who sustained chronic radiation morbidity had thin physiques. The maximum likelihood multiple logistic model was utilized to predict the probability of enteric injury as a function of thin physique, previous operations, and hypertension for individual patients. The usefulness of predictive models is discussed, and possible reasons for the susceptibility of thin women to ionizing radiation are explored.

Adolescent↗

PubMed1989

Use of a four-parameter logistic model to evaluate the quality of the protein from three insect species when fed to rats.

The quality of three insect protein sources [Mormon cricket meal (MCM), house cricket meal (HCM) and Eastern tent caterpillar meal (TCM)] was evaluated relative to that of lactalbumin (LA) and soy protein (SP) by using both amino acid analysis and a rat bioassay. The amino acid pattern of the three insect meals indicated that methionine should be the first limiting amino acid for growing rats. In the rat bioassay, weanling Sprague-Dawley rats were fed graded levels of the five proteins in purified diets and the response (weight or nitrogen gain) evaluated as a function of nitrogen intake. The individual nitrogen intake-animal response results could be described by a series of curves using a four-parameter logistic model. The use of parameter sharing permitted the full range of responses to be described so that statistical differences between the dose-response curves could be identified. When used for either weight maintenance, nitrogen equilibrium, maximum weight gain or maximum nitrogen retention, the five protein sources could be ranked in the following order: LA greater than HCM greater than MCM = SP greater than TCM. Relative to lactalbumin, the value of all four protein sources decreased with increasing nitrogen intake. The low values obtained for TCM may have been related to factors other than protein quality. The results of this study indicate that some insect proteins are equivalent or superior to soy protein as a source of amino acids for growing rats.

Amino Acids↗

PubMed2006

Random effects logistic models for analysing efficacy of a longitudinal randomized treatment with non-adherence.

We present a random effects logistic approach for estimating the efficacy of treatment for compliers in a randomized trial with treatment non-adherence and longitudinal binary outcomes. We use our approach to analyse a primary care depression intervention trial. The use of a random effects model to estimate efficacy supplements intent-to-treat longitudinal analyses based on random effects logistic models that are commonly used in primary care depression research. Our estimation approach is an extension of Nagelkerke et al.'s instrumental variables approximation for cross-sectional binary outcomes. Our approach is easily implementable with standard random effects logistic regression software. We show through a simulation study that our approach provides reasonably accurate inferences for the setting of the depression trial under model assumptions. We also evaluate the sensitivity of our approach to model assumptions for the depression trial.

Humans↗

PubMed1992

[Logistic model for predicting the prognosis in patients with intra-abdominal infection based on the APACHE II index].

BACKGROUND: The APACHE II method has been widely used to classify patients according to disease severity. The high mortality and the lack of reliable prognostic parameters justify the study and application of indexes of severity (IS) and prognostic indexes (PI) in patients with intraabdominal sepsis. METHODS: A prospective study is presented concerning 100 patients with intraabdominal sepsis in whom a prognostic index derived from the APACHE II method by means of a logistic regression model was applied. In this model the APACHE II score is used as the only independent variable with the aim of predicting the outcome (mortality or survival) at the time of hospital admission. RESULTS: The predictive values obtained, with a 70% probability of mortality taken as the cut-off point, were: sensitivity 100%, specificity 87.7% and total predictive capacity 91%. CONCLUSIONS: It was concluded that the logistic prediction model of prognosis shows a high correlation with patient outcome and the application of the APACHE II score is useful in patients with intraabdominal infection.

Abdomen↗

PubMed1998

A logistic model of the seasonal migration decision for elderly households in Arizona and Minnesota.

While most previous studies of elderly migration have investigated permanent migration using Census data, this paper employs household (micro) data from statewide surveys conducted in Arizona and Minnesota to analyze seasonal migration as an economic decision. Estimation of logistic regression models for each state indicate income and age are important determinants, whereas these variables have not proven significant in previous studies based on aggregate data. The results lead to the conclusion that seasonal migration may be an integral part of a life cycle of elderly migration.

Aged↗

PubMed1982

A logistic model based on enzyme activities for the prediction of response of breast cancer patients to chemotherapy.

A logistic regression model, utilizing the activities of certain selected glycolytic enzymes and ER status measured on primary or recurrent lesions, has been applied to predict for response to combination chemotherapy regimens administered to women with advanced breast cancer. The clinical outcome of response or no response was evaluated retrospectively using criteria employed by cooperative group protocols. In 93 cases, 58/61 patients classified as nonresponders and 22/32 patients demonstrating objective responses would have been correctly designated, based on the 50% estimated probability as the level for separation of responders from nonresponders. The overall predictive accuracy of this model was 86%, with apparently greater accuracy for prediction of lack of response. Addition of estrogen receptor status to the model imparted no gain in accuracy of prediction. Application of this model to a prospective study is warranted.

Adult↗

PubMed1988

Correspondence analysis and logistic modelling: complementary use in the analysis of a health survey among nurses.

Logistic or other modelling approaches are often appropriate for studying epidemiological data. However, health surveys may be more complex. With numerous variables, there is a need for exploratory analysis. Parsimonious description of the data is also a useful complement to modelling. Correspondence analysis may be useful in such exploratory phases. An example of the complementary use of the two approaches is presented in the context of a health survey among nurses, which focused on the relationship between shift and night work, and declared health problems.

Adult↗

PubMed1996

The application of a log-logistic model to describe the thermal inactivation of Clostridium botulinum 213B at temperatures below 121.1 degrees C.

In this work, the death of Clostridium botulinum 213B was measured at temperatures between 101 degrees C and 121 degrees C. It was found that at all temperatures tested, survivor curves deviated from log-linearity which prevented their description using traditional first order kinetics. The survivor curves were better described using a vitalistic approach and the log-logistic transformation proposed by Cole et al. (1993). A single equation was derived to describe all survivor curves over the temperature range tested and a comparison of predicted and measured data showed good correlation. The implications of the use of the vitalistic approach to the validity of the 'minimum botulinum cook' is discussed.

Clostridium botulinum↗